Abstract:

A display device comprises a metallic wiring formed on an insulating
substrate, an inorganic insulating film formed on the metallic wiring, an
organic resin film formed on the inorganic insulating film, a transparent
conductive film formed in a portion on the metallic wiring where the
inorganic insulating film and the organic resin film are removed, a
connection terminal formed in a region for mounting a driving IC external
to the display region on the insulating substrate, and a bump of the
driving IC connected to the connection terminal by an anisotropic
conductive film in order to supply a signal to the display region. The
region for mounting a driving IC includes a region where the inorganic
insulating film and the organic resin film are formed on the metallic
wiring and a region where the inorganic insulating film and the organic
resin film are removed from the metallic wiring.

Claims:

1. A display device comprising:an insulating substrate on which a display
region is formed;a metallic wiring formed on the insulating substrate;an
inorganic insulating film formed on the metallic wiring;an organic resin
film formed on the inorganic insulating film;a transparent conductive
film formed in a portion on the metallic wiring where the inorganic
insulating film and the organic resin film are removed;a connection
terminal formed in a driving IC mounting region external to the display
region on the insulating substrate; anda bump of the driving IC connected
to the connection terminal by an anisotropic conductive film for
supplying a signal to the display region,wherein the driving IC mounting
region includes a region where the inorganic insulating film and the
organic resin film are formed on the metallic wiring and a region where
the inorganic insulating film and the organic resin film are removed from
the metallic wiring, andwherein at least an end portion of the connection
terminal is covered by the transparent conductive film or the inorganic
insulating film.

2. The display device according to claim 1, wherein the inorganic
insulating film and the organic resin film are removed with the same
mask.

3. The display device according to claim 1, wherein the inorganic
insulating film formed on the metallic wiring covers the upper surface
and side surfaces of the metallic wiring.

4. The display device according to claim 1,wherein the driving IC is
replaced with a flexible circuit board composed of a polyimide film and
copper foil wiring, andwherein the connection terminal on the insulating
substrate is connected to the terminal on the flexible circuit board via
an anisotropic conductive film.

5. A display device comprising:an insulating substrate on which a display
region is formed;metallic wiring formed on the insulating substrate;an
inorganic insulating film formed on the metallic wiring;an organic resin
film formed on the inorganic insulating film;a transparent conductive
film formed in a portion on the metallic wiring where the inorganic
insulating film and organic resin film are removed;a connection terminal
formed in a driving IC mounting region external to the display region on
the insulating substrate; anda bump of the driving IC connected to the
connection terminal by an anisotropic conductive film in order to supply
a signal to the display region,wherein the inorganic insulating film and
the organic resin film in a region except the metallic wiring are removed
in the driving IC mounting region.

6. The display device according to claim 5, wherein the inorganic
insulating film and the organic resin film in a region except the
metallic wiring and the edge part of the connection terminal are removed
in the driving IC mounting region.

Description:

[0001]This application claims priority from Japanese Patent Application
No. 2007-267801 filed on Oct. 15, 2007, the entire subject matter of
which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to a display device including an
organic resin film and in particular to a connection structure for
mounting a driving circuit (driving IC) on the periphery of a display
region.

[0004]2. Description of the Related Art

[0005]For example, a display device using liquid crystal includes two
insulating (for example glass) substrates with liquid crystal sandwiched
therebetween and a driving IC connected to the end of the insulating
substrates, the insulating substrates arranged on a planar light source
device called a backlight. For example, in a liquid crystal display
device using a thin-film transistor (TFT), thin-film transistors are
arranged in a matrix shape on one substrate (TFT array substrate) out of
the two insulating substrates and the substrate is overlaid on the other
substrate (CF substrate) with the external shape protruding beyond the
same. Further, in the case of a reflective or semi-transparent type
liquid crystal display device, a reflection electrode layer composed of
an organic resin film is formed to form a reflection electrode including
asperities on a TFT array substrate. Each TFT includes a pixel formed
thereon. An image signal transmitted to a pixel is controlled by turning
ON or OFF the TFT. Source wiring for inputting an image signal from the
source electrode of each TFT is drawn to the end of a glass substrate.
Near the end of the TFT array substrate is formed a pad (connection
terminal) for connecting a driving IC. The inorganic insulating film
layer is removed from the surface of the pad and a transparent conductive
film is formed on the exposed source wiring material.

[0006]Gate wiring for turning ON/OFF the TFT is drawn from the gate
electrode of each TFT to the end of the TFT substrate. Near the end of
the TFT array substrate is formed a pad (connection terminal) for
connecting a driving IC, same as the source side. For example, in a
configuration where a driving IC is mounted by a flip-chip mounting
method, a driving IC is directly mounted on the connection terminal in a
mounting region arranged in a portion where the TFT array substrate at
the panel end is protruding by way of an adhesive resin including
conductive particles dispersed therein called ACF (anisotropic conductive
film). At the end of the wiring arranged near the driving IC on the TFT
array substrate closer to the end the TFT array substrate is formed a
pad. To the pad is connected an FPC (flexible printed circuit board) via
an ACF. The FPC is connected to a circuit board for controlling a driving
IC. A control signal and a power for the driving IC are inputted to the
driving IC via the wiring on the FPC and the wiring on the TFT array
substrate. There may be a case where a driving IC is directly connected
to a terminal formed on a TFT array substrate instead of an FPC.

[0007]In the related art, an example of a driving IC connecting structure
of a liquid crystal display device using an organic resin film such as a
reflective type liquid crystal display device does not form an organic
resin film in the connecting portion of a driving IC and covers its
surface with an inorganic insulating film layer alone (for example, refer
to JP-A-2000-171817 (FIG. 2)).

[0008]With the driving IC connecting structure in the related art, it is
necessary to provide a larger region where an organic resin film is
removed than a region where an inorganic insulating film is removed in
order to form a connection terminal on an insulating substrate. Thus, it
is necessary to separately provide a process for removing an organic
resin film and a process for removing an inorganic insulating film. This
adds to the number of manufacturing processes and manufacturing costs.
Another approach is to remove an organic resin film and an inorganic
insulating film broadly over the periphery of a driving IC by using the
same mask. In case this method is used, all the metallic wiring is
exposed in a portion where the organic resin film and the inorganic
insulating film are removed, resulting in reduced insulating properties
between wires or corrosion of wiring. Another approach is to remove only
the connection terminals of an organic resin film and an inorganic
insulating film at the same time by using the same pattern. This method
presents a problem that the bonding strength between the anisotropic
conductive film for connection and the organic resin film is lower than
that between the anisotropic conductive film and the inorganic insulating
film thus reducing the connection reliability.

SUMMARY OF THE INVENTION

[0009]The invention has been accomplished in view of the above problems.
An object of the invention is to provide a display device free from an
increase in the production costs related to pattern formation of an
organic resin film and an inorganic insulating film, reduced insulating
properties and corrosion caused by exposure of a wiring pattern, or
reduction in the connection reliability of a driving IC unlike in the
related art.

[0010]The invention provides a display device comprising: an insulating
substrate on which a display region is formed; metallic wiring formed on
the insulating substrate; an inorganic insulating film formed on the
metallic wiring; an organic resin film formed on the inorganic insulating
film; a transparent conductive film formed in a portion on the metallic
wiring where the inorganic insulating film and organic resin film are
removed; a connection terminal formed in a driving IC mounting region
external to the display region on the insulating substrate; and the bump
of the driving IC connected to the connection terminal by an anisotropic
conductive film in order to supply a signal to the display region;
characterized in that the driving IC mounting region includes a region
where the inorganic insulating film and the organic resin film are formed
on the metallic wiring and a region where the inorganic insulating film
and the organic resin film are removed from the metallic wiring.

[0011]With the invention, it is possible to obtain a display device free
from an increase in the production costs related to pattern formation of
an organic resin film and an inorganic insulating film or reduced
insulating properties and corrosion caused by exposure of a wiring
pattern, and featuring improved connection reliability of a driving IC.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a general external view of a display device according to
Embodiment 1 of the invention;

[0013]FIG. 2 is a cross-sectional view of a driving IC mounting part of a
display device according to Embodiment 1 of the invention;

[0014]FIG. 3 is a cross-sectional view of a driving IC mounting part of a
display device according to Embodiment 2 of the invention; and

[0015]FIG. 4 is a cross-sectional view of a driving IC mounting part of a
display device according to Embodiment 3 of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1

[0016]Embodiment 1 of the invention will be described referring to FIGS. 1
and 2. FIG. 1 is a general external view of a display device according to
Embodiment 1 of the invention. FIG. 2 is a cross-sectional view of a
driving IC mounting part of a display device according to Embodiment 1 of
the invention.

[0017]Referring to FIG. 1, an insulating substrate (TFT array substrate) 1
and a counter substrate (CF substrate) 2 both formed by glass or the like
are overlaid one on the other, and a polarizer 3 is bonded to the
external surface thereof. The insulating substrate 1 includes a part
protruding further outward than the counter substrate 2. On the
protruding part is formed a region for mounting a circuit member such as
a driving IC 4. In the region for mounting a driving IC 4, an anisotropic
conductive film (for example ACF: an isotropic conductive film) 5 is
bonded on a connection terminal formed on the insulating substrate 1. On
the anisotropic conductive film is mounted a driving IC 4 for driving
liquid crystal. In an outward region closer to the substrate end than the
driving IC 4 mounted on the insulating substrate 1 is bonded an
anisotropic conductive film 5, same as the driving IC 4, and a flexible
circuit board 6 is mounted on the anisotropic conductive film 5.

[0018]FIG. 2 is a cross-sectional view of a part for mounting a driving IC
4 on the insulating substrate 1 of a display device 100 according to the
invention shown in FIG. 1. A connection terminal 7 composed of a metal is
formed in a region on the insulating substrate 1 where the driving IC 4
is mounted. A transparent conductive film 10 is formed in a region where
the inorganic insulating film 12 and the organic resin film 13 are
removed from the connection terminal 7. The bump 9 of the driving IC 4 is
connected onto the transparent conductive film 10 via conductive
particles 8 of an anisotropic conductive film 5. The conductive particles
8 are dispersed in the anisotropic conductive film 5 and are generally
composed of spherical plastics 3 to 5 μm in diameter with Ni plating
or Au plating applied thereon. The anisotropic conductive film 5 is a
thermosetting resin including conductive particles 8 distributed therein
and formed into a film. The bump 9 of the driving IC 4 and the insulating
substrate 1 sandwich, heat and pressurize the anisotropic conductive film
5 to harden the thermosetting resin in the anisotropic conductive film 5
to cause the anisotropic conductive film 5 to be mechanically held on the
insulating substrate 1 and electrically connected to the transparent
conductive film 10 on the connection terminal 7. On metallic wiring 11
that is likely to affect the quality are formed an inorganic insulating
film 12 and an organic resin film 13. An inorganic insulating film 12 and
an organic resin film 13 are formed in a region external to the region
for mounting a driving IC 4.

[0019]The portion of the mounting region except the metallic wiring 11
includes a portion where the inorganic insulating film 12 and the organic
resin film 13 are removed. The surface of the insulating substrate 1 or
metallic wiring 14 that is unlikely to affect the quality and the
anisotropic conductive film 5 are in direct contact with each other. The
metallic wiring 11 that is likely to affect the quality refers to, for
example, wiring with a high potential, wiring with a large potential
difference from adjacent wiring, wiring with a potential difference from
adjacent wiring and close to the same, wiring vulnerable to corrosion, or
relatively thin wiring compared with other wiring. The metallic wiring
that is unlikely to affect the quality refers to, for example, an
alignment mark, wiring to which a potential is not applied or wiring made
of a material that is less vulnerable to corrosion. The term "metallic
wiring" used herein includes wiring to which any potential is supplied as
well as an alignment mark or a floating pattern composed of a metallic
film. The inorganic insulating film 12 and the organic resin film 13 are
removed from the metallic wiring 14 that is unlikely to affect the
quality in the region for mounting a driving IC 4. To enhance the
connection reliability of a driving IC 4, it is thus preferable to
remove, if possible, the inorganic insulating film 12 and the organic
resin film 13 from the metallic wiring 14 that is unlikely to affect the
quality. This reduces the portion where the anisotropic conductive film 5
is in direct contact with the organic resin film 13 in the mounting
region thus reliably connecting the driving IC 4 and the TFT array
substrate 1 with each other.

[0020]On the edge part of the connection terminal 7 shown in FIG. 2, the
inorganic insulating film 12 and the organic resin film 13 may be removed
across the entire electrode like the connection terminal 7 on the
left-hand side of FIG. 2, or the inorganic insulating film 12 and the
organic resin film 13 may remain on the periphery of the connection
terminal 7 as shown by the connection terminal 7 on the right-hand side
of FIG. 2.

[0021]Next, processes for manufacturing a display device 100 shown in
FIGS. 1 and 2 will be described. A first metallic film serving as a scan
line or a storage capacity line is formed on the insulating substrate 1.
The first metallic film is formed by a thin film made of a material such
as Al, Cr, Cu, Ta, or Mo, or an alloy of one of these and another
substance. Next, a photolithography process is used to pattern the first
metallic film to form the metallic wiring 11 or the metallic wiring 14
serving as a scan line or a storage capacity line and the connection
terminal 7.

[0022]After that, a film forming device such as a plasma CVD device is
used to successively form a gate insulating film, a semiconductor film,
and an ohmic contact film. The gate insulating film may be SiNx, SiOx, or
SiOxNy as an inorganic insulating film or a laminate film of these. The
semiconductor film may be made of amolphous silicon (a-Si) or polysilicon
(p-Si). The ohmic contact film uses n-a-Si or n-p-Si formed by an a-Si
film or a p-Si film into which a small amount of phosphor (P) or the like
is doped. The photolithography process is used to pattern the
semiconductor film and the ohmic contact film by way of dry etching or
the like.

[0023]Next, a second metallic film serving as a picture signal line is
formed. The second metallic film is formed by a thin film made of a
material such as Al, Cr, Cu, Ta, or Mo, or an alloy of one of these and
another substance, a laminate of heterogeneous metallic films, or a thin
film of different compositions in the film thickness direction. Next, a
photolithography process is used to form the metallic wiring 11 or 14
serving as a picture signal line. In the process of patterning the
picture signal line, a source electrode and a drain electrode are formed
at the same time. The connection terminal 7 may be formed by the second
metallic film.

[0024]An inter-layer insulating film is formed on a film forming device
such as a plasma CVD device. Same as the gate insulating film, the
inter-layer insulating film may use SiNx, SiOX, or SiOxNy, or a laminate
film of these. Next, an organic resin film is formed and the organic
resin film, gate insulating film and inter-layer insulating film are
patterned with the same mask in a photolithography process. After that, a
contact hole is formed by the collective patterning of the organic resin
film, inter-layer insulating film and gate insulating film. The drain
electrode is electrically continued to a pixel electrode (described
later) via the contact hole. It is thus made possible to remove the gate
insulating film, inter-layer insulating film and organic resin film on
the metallic wiring 14 that is unlikely to affect the quality and the
connection terminal 7. In this case, at least the inorganic insulating
film 12 is preferably patterned so as to reliably cover the entirety of
the upper surface and side surfaces of the metallic wiring 11 as shown in
FIG. 4. Further, the inorganic insulating film 12 formed on the side
surface of the metallic wiring 11 preferably has a thickness of at least
3 μm in the direction level with respect to the insulating substrate
1. With this configuration, it is possible to reliably prevent corrosion
of the metallic wiring 11. After that, a reflection electrode is formed
and patterned in a display device including a reflective liquid crystal
display.

[0025]A conductive thin film as a transparent metal such as ITO or
SnO2 serving as a pixel electrode is formed on the inter-layer
insulating film. In a photolithography process, the conductive thin film
is patterned so as to be surrounded by a scan line, a storage capacity
line and a picture signal line to complete an insulating substrate on
which a TFT or the like is formed.

[0026]In FIGS. 1 and 2, the inorganic insulating film 12 is composed of
the gate insulating film and the inter-layer insulating film. The
metallic wiring 11, 14 and the connection terminal 7 are formed by either
the first metallic film or the second metallic film or both of them. The
inorganic insulating film 12 and the organic resin film 13 formed by a
gate insulating film and an inter-layer insulating film may be patterned
with the same mask. The inorganic insulating film may be formed by a
single layer of either a gate insulating film or an inter-layer
insulating film instead of both. For the metallic wiring composed of the
first metallic wiring or the second metallic wiring, it is determined
whether to remove an inorganic insulating film and an organic resin film
depending on whether the metallic wiring is likely to affect the quality
as described above.

[0027]While a transparent conductive film 10 is formed on the connection
terminal 7 and the transparent conductive film 10 is connected to the
bump 9 of the driving IC 4 via the anisotropic conductive film 5 in FIGS.
1 and 2, the connection terminal 7 may be directly connected to the bump
9 of the driving IC 4 via the anisotropic conductive film 5.

With this configuration, it is possible to pattern an organic resin film
and an inorganic insulating film with the same mask without increasing
the production costs, suppress reduction in the insulating properties and
corrosion caused by exposure of metallic wiring, and reduce the area of
the portion where an anisotropic conductive film and an organic resin
film are in direct contact with each other in a mounting region. It is
thus possible to obtain a display device free from reduction in the
connection reliability of a driving IC.

Embodiment 2

[0028]Embodiment 2 of the invention will be described referring to FIG. 3.
FIG. 3 is a cross-sectional view of a driving IC mounting part of a
display device according to Embodiment 2 of the invention. In FIG. 3, a
component same as that in FIGS. 1 and 2 is given the same sign and
differences from Embodiment 1 will be described.

[0029]In FIG. 3, a flexible circuit board 15 composed of a polyimide film
and copper foil wiring is mounted in place of a driving IC in Embodiment
1. In FIG. 3, the lead terminal 16 of the flexible circuit board 15 is
connected to the transparent conductive film 10 on the connection
terminal 7 via the anisotropic conductive film 5. In a region of the
flexible circuit board 15 external to the mounting region are formed an
inorganic insulating film 12 and an organic resin film 13. As shown by
the connection terminals 7 on the left-side and in the center of FIG. 3,
the inorganic insulating film 12 and the organic resin film 13 may be
removed across the entire electrode on the edge part of the connection
terminal 7. Or, as shown by the connection terminal 7 on the rightmost
side of FIG. 3, the inorganic insulating film 12 and the organic resin
film 13 may remain on the periphery of the electrode. For the metallic
wiring 11, 14 also, in case the metallic wiring is formed in the region
for mounting a flexible circuit board 15 in this embodiment, the same
configuration as Embodiment 1 may be employed to provide the same working
effect as Embodiment 1.

[0030]With the above configuration, also in case a flexible circuit board
is mounted on an insulating substrate, it is possible to pattern an
organic resin film and an inorganic insulating film with the same mask
without increasing the production costs, suppress reduction in the
insulating properties and corrosion caused by exposure of metallic
wiring, and reduce the area of the portion where an anisotropic
conductive film and an organic resin film are in direct contact with each
other in amounting region, thereby obtaining a display device free from
reduction in the connection reliability of a flexible circuit board.

Embodiment 3

[0031]Embodiment 3 of the invention will be described referring to FIG. 4.
FIG. 4 is a cross-sectional view of a driving IC mounting part of a
display device according to Embodiment 3 of the invention. In FIG. 4, a
component same as that in FIGS. 1 to 3 is given the same sign and
differences from Embodiments 1 or 2 will be described.

[0032]In Embodiments 1 and 2, also for the metallic wiring 14 that is
unlikely to affect the quality, it is assumed that a reflection electrode
is formed by an alloy of the same system as the metallic wiring 14 (for
example an Al alloy or a metal group etched with the etching liquid of
the same system) and patterned after the metallic wiring 14 is patterned.
In case an inorganic insulating film and an organic resin film on the
metallic wiring 14 have been removed, the metallic wiring 14 is etched at
the same time. In case only a metal vulnerable to corrosion is used as a
material of the metallic wiring, the metallic wiring may be more likely
to be corroded in the absence of an inorganic insulating film and an
organic resin film on the metallic wiring. As a countermeasure, as shown
in FIG. 4, a configuration may be employed where an inorganic insulating
film 12 and an organic resin film 13 remain on the metallic wiring 11 and
14 alone in the region where the driving IC 4 is mounted and the
inorganic insulating film 12 and the organic resin film 13 are removed
substantially across the entirety of the remaining region. The inorganic
insulating film 12 and the organic resin film 13 may remain on the edge
part on the connection terminal 7 (shown by the connection terminal on
the right-hand side of FIG. 3).

[0033]With this configuration, metallic wiring is not etched when a
reflection electrode is formed by an alloy of the same system as the
metallic wiring following the process of patterning the metallic wiring.
The metallic wiring is free from corrosion even in case only a metal
vulnerable to corrosion is used as a material of the metallic wiring. In
the region for mounting a driving IC except the metallic wiring portion,
an inorganic insulating film and an organic resin film are removed
substantially over the entire portion, so that the region where an
anisotropic conductive film and an organic resin film are in direct
contact with each other can be reduced. It is thus possible to obtain a
display device free from reduction in the connection reliability of a
driving IC.

[0034]Same as Embodiment 1, the inorganic insulating film 12 is preferably
patterned so as to reliably cover the entirety of the upper surface and
side surfaces of the metallic wiring 11, 14 as shown in FIG. 4. Further,
the inorganic insulating film 12 formed on the side surface of the
metallic wiring 11, 14 preferably has a thickness of at least 3 μm in
the direction level with respect to the insulating substrate 1. With this
configuration, it is possible to reliably prevent corrosion of the
metallic wiring 11, 14. While a driving IC is mounted in this embodiment,
a flexible circuit board may be mounted in place of a driving IC, same as
Embodiment 2.

[0035]While a display device using liquid crystal has been described in
the foregoing embodiments, the invention is not limited thereto but is
applicable to any display device using an electroluminescence element or
the like as well as to any device where a driving circuit or a flexible
circuit board is connected via an anisotropic conductive film to a device
where an inorganic insulating film and an organic resin film are formed
on an insulating substrate.